SPring-8

Date&Time: 11th November 2003, 13:30-14:20

Speaker: Prof. Errki Ikonen
Affiliation: Helsinki University of Technology

Abstract
　　A simple model to analyze excess coincidences of photons can be presented using the rapidly fluctuating interference pattern of two incoherent plane waves and their randomly varying phase difference. The excess coincidences appear as a non-vanishing term in the product of the interference patterns when averaged over the random phase difference. Early experiments of this intensity correlation were performed with visible light from distant stars, where it could be applied to measurement of the angular diameters. A more recent development is related to coincidences of signal and idler photons in spontaneous parametric down conversion of laser light. These experiments have the special feature that they can demonstrate the non-classical character of the radiation field, requiring quantum field theory to explain the results of the experiments.
　　With visible light it is relatively straightforward to produce conditions where excess coincidences can be observed. All this becomes much more difficult at shorter wavelengths. Thus it is only recently that the intensity correlation effects were observed with hard x rays. The talk is concluded with a brief summary of the results obtained at SPring-8.